Python Basics (2023-05-15 - 2023-05-17)

code = '[1,2,3]'

type(code)

str

blah blah

eval(code)

[1, 2, 3]

Syntax etc.

def add(a, b):
    'Complex algorithm to add two numbers'
    return a+b

print(type(add))

<class 'function'>

add.__doc__

'Complex algorithm to add two numbers'

help(add)

Help on function add in module __main__:

add(a, b)
    Complex algorithm to add two numbers

class Foo:
    'pointless class'

Foo.__doc__

'pointless class'

help(Foo)

Help on class Foo in module __main__:

class Foo(builtins.object)
 |  pointless class
 |
 |  Data descriptors defined here:
 |
 |  __dict__
 |      dictionary for instance variables (if defined)
 |
 |  __weakref__
 |      list of weak references to the object (if defined)

Was ist das mit __?

class Bar:
    def __init__(self, param):
        self.member = param

b = Bar(42)

class Bar:
    def __init__(self, param):
        self.member = param
    def doSomething(self):
        return self.member**2

b = Bar(42)
b.doSomething()

1764

print(b)

<__main__.Bar object at 0x7fe7fbf80df0>

class Bar:
    def __init__(self, param):
        self.member = param
    def doSomething(self):
        return self.member**2
    def __str__(self):
        return f'Ein nettes sinnloses Objekt mit dem Wert {self.member}'

b = Bar(42)

print(b)

Ein nettes sinnloses Objekt mit dem Wert 42

Variables

a = 42

print(type(a))

<class 'int'>

a = 1.5

print(type(a))

<class 'float'>

a = 'blah'

print(type(a))

<class 'str'>

a = [1,2,3]
print(type(a))

<class 'list'>

Tuple unpacking

a = 1
b = 2

a

1

b

2

a, b = 1, 2

x = 1, 2

print(type(x))

<class 'tuple'>

x

(1, 2)

try:
    a, b, c = 1, 2
except Exception as e:
    print(e, type(e))

not enough values to unpack (expected 3, got 2) <class 'ValueError'>

print('hier bin ich')

hier bin ich

a, b

(1, 2)

tmp = a
a = b
b = tmp

a, b

(2, 1)

a, b = b, a

a, b

(1, 2)

Object Identity

a = 42

id(a)

140634424624656

b = a

id(b)

140634424624656

b = 7

id(b)

140634424623536

id(a)

140634424624656

Datatypes

i = 42

i = -42

i

-42

i = 0o644

i

420

i = 0xdeadbeef

i

3735928559

i = 0b01110101

i

117

i = 2**64-1

bin(i)

'0b1111111111111111111111111111111111111111111111111111111111111111'

len(bin(i))

66

i += 1

i

18446744073709551616

len(bin(i))

67

10**1000

10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

3/2

1.5

3//2

1

l1 = [1,2,3]
l2 = [2,3,4]
try:
    l1*l2
except Exception as e:
    print(e, type(e))

can't multiply sequence by non-int of type 'list' <class 'TypeError'>

l1 + l2

[1, 2, 3, 2, 3, 4]

Datatype Conversions

i = 42

s = str(i)

s

'42'

i.__str__()

'42'

i.__float__()

42.0

f = float(i)

f

42.0

int(f)

42

f.__int__()

42

s = '42'

int(s)

42

int(s, 16)

66

s = '0xdeadbeef'

try:
    int(s)
except Exception as e:
    print(e, type(e))

invalid literal for int() with base 10: '0xdeadbeef' <class 'ValueError'>

int(s, 16)

3735928559

1 + 2.3

3.3

try:
    '1' + 2
except Exception as e:
    print(e, type(e))

can only concatenate str (not "int") to str <class 'TypeError'>

try:
    '1'.__add__(2)
except Exception as e:
    print(e, type(e))

can only concatenate str (not "int") to str <class 'TypeError'>

Difference between ctor and eval()?

int('42')

42

eval('42')

42

s = '[1,2,3]'

list(s)

['[', '1', ',', '2', ',', '3', ']']

eval(s)

[1, 2, 3]

code = '''
i = 0
while i<42:
    i+=1
print(i)
'''

type(code)

str

exec(code)

42

config = '''
SETTING_BLAH = 42
SETTING_FOO = 'jo oida'
'''

config_context = {}

exec(config, config_context)

config_context['SETTING_BLAH']

42

Immutable vs. Mutable

def foo(a):
    print(id(a))

x = 666

id(x)

140634341074320

foo(x)

140634341074320

x = 42

id(x)

140634424624656

x += 1

id(x)

140634424624688

x = 42

id(x)

140634424624656

x = 1234

y = 1234

x is y

False

id(x)

140634341076688

id(y)

140634341077776

Memory Management

abc = 666

del abc

try:
    abc
except Exception as e:
    print(e, type(e))

name 'abc' is not defined <class 'NameError'>

f = open('/etc/passwd')

f.close()

with open('/etc/passwd') as f:
    print(len(list(f)))

48

Compound Datatypes

List, Tuple

l = [1,2,'drei']

len(l)

3

l.append(4)

len(l)

4

l

[1, 2, 'drei', 4]

l1 = [5, 'sechs']

l.extend(l1)

l

[1, 2, 'drei', 4, 5, 'sechs']

l.append(l1)

l

[1, 2, 'drei', 4, 5, 'sechs', [5, 'sechs']]

l.reverse()

l

[[5, 'sechs'], 'sechs', 5, 4, 'drei', 2, 1]

l += l1

l

[[5, 'sechs'], 'sechs', 5, 4, 'drei', 2, 1, 5, 'sechs']

t = (1,2,'drei')

try:
    t.append(4.0)
except Exception as e:
    print(e, type(e))

'tuple' object has no attribute 'append' <class 'AttributeError'>

t1 = (5, 'sechs')

id(t)

140634343012864

t += t1

id(t)

140634341099856

The `in`` operator

l = [3,4,1,'fuenf']

3 in l

True

5 not in l

True

not 5 in l

True

'fuenf' in l

True

6 in l

False

Dictionary

d = {'one': 1, 'two': 2, 3: 'three'}

d['one']

1

try:
    d['three']
except Exception as e:
    print(e, type(e))

'three' <class 'KeyError'>

'three' in d

False

value = d.get('three')

print(value)

None

d['three'] = 3

'three' in d

True

del d['three']

'three' in d

False

d

{'one': 1, 'two': 2, 3: 'three'}

Set

s = {1,2,'drei'}

s.add(4.0)

s.remove('drei')

2 in s

True

l = [1,2,3]

s.add(l)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/tmp/ipykernel_61373/1125713270.py in <module>
----> 1 s.add(l)

TypeError: unhashable type: 'list'

i = 42
i.__hash__()

i = 1234567876543234567654321234565432123456
i.__hash__()

s.add((1,2,3))

Slicing

l = [2,3,4,5,6]

l[2:4]

l[2:5]

l[2:len(l)]

l[2:len(l)-1]

l[2:-1]

l[1]

l[1]

l[0]

try:
    l[len(l)]
except Exception as e:
    print(e, type(e))

l[len(l)-1]

l[-1]

l[0:6]

l[0:]

l[:]

l[1:]

for

for name in ['Caro', 'Johanna', 'Eva', 'Jörg']:
    print(name)

Caro
Johanna
Eva
Jörg

l = [0,1,2,3,4]
for elem in l:
    print(elem)

0
1
2
3
4

for elem in range(5):
    print(elem)

0
1
2
3
4

r = range(5)

print(type(r))

<class 'range'>

Iterator Protocol

r = range(3)

it = iter(r)

next(it)

0

next(it)

1

next(it)

2

try:
    next(it)
except Exception as e:
    print(e, type(e))

 <class 'StopIteration'>

l = [0,1,2]

it = iter(l)

next(it)

0

next(it)

1

next(it)

2

try:
    next(it)
except Exception as e:
    print(e, type(e))

 <class 'StopIteration'>

def my_range(n):
    current = 0
    yield current
    while current < n:
        yield current
        current += 1

r = my_range(3)

print(type(r))

<class 'generator'>

it = iter(r)

next(it)

0

next(it)

0

next(it)

1

next(it)

2

try:
    next(it)
except Exception as e:
    print(e, type(e))

 <class 'StopIteration'>

The range Function

for elem in range(3):
    print(elem)

0
1
2

for elem in range(0,3):
    print(elem)

0
1
2

for elem in range(1,4):
    print(elem)

1
2
3

for elem in range(1,7,2):
    print(elem)

1
3
5

list('abc')

['a', 'b', 'c']

for elem in 'abc':
    print(elem)

a
b
c

for elem in range(3):
    print(elem)

0
1
2

list(range(3))

[0, 1, 2]

for elem in ['Joerg', 'Johanna', 'Caro', 'Philipp', 'Eva']:
    print(elem)

Joerg
Johanna
Caro
Philipp
Eva

i = 0
for elem in ['Joerg', 'Johanna', 'Caro', 'Philipp', 'Eva']:
    print(i, elem)
    i += 1

0 Joerg
1 Johanna
2 Caro
3 Philipp
4 Eva

for elem in enumerate(['Joerg', 'Johanna', 'Caro', 'Philipp', 'Eva']):
    print(elem)

(0, 'Joerg')
(1, 'Johanna')
(2, 'Caro')
(3, 'Philipp')
(4, 'Eva')

for elem in enumerate(['Joerg', 'Johanna', 'Caro', 'Philipp', 'Eva']):
    pos = elem[0]
    name = elem[1]
    print(pos, name)

0 Joerg
1 Johanna
2 Caro
3 Philipp
4 Eva

for pos, name in enumerate(['Joerg', 'Johanna', 'Caro', 'Philipp', 'Eva']):
    print(pos, name)

0 Joerg
1 Johanna
2 Caro
3 Philipp
4 Eva

for pos, elem in enumerate(range(3, 7)):
    print(pos, elem)

0 3
1 4
2 5
3 6

References, (Im)mutability

a = 42

b = a

id(a), id(b)

(140634424624656, 140634424624656)

a = 666

b

42

id(a)

140634281233520

id(b)

140634424624656

l1 = [1,2,3]

l2 = l1

l2.append(4)

l2

[1, 2, 3, 4]

l1

[1, 2, 3, 4]

l1 = [1,2,3]
l2 = l1[:]

id(l1), id(l2)

(140634341798400, 140634341995008)

l1 = [1, ['a', 'b'], 2]

id(l1)

140634341576640

l2 = l1[:]

id(l2)

140634341773312

l1.append(3)

l1

[1, ['a', 'b'], 2, 3]

l2

[1, ['a', 'b'], 2]

l1[1]

['a', 'b']

l2[1]

['a', 'b']

l1[1].append('c')

l1

[1, ['a', 'b', 'c'], 2, 3]

l2

[1, ['a', 'b', 'c'], 2]

id(l1[1])

140634281802304

id(l2[1])

140634281802304

Functions

def foo(a):
    return a**2

print(type(foo))

<class 'function'>

x = foo

x(2)

4

foo = 666

try:
    foo(2)
except Exception as e:
    print(e, type(e))

'int' object is not callable <class 'TypeError'>

global_variable = 666

def bar():
    print(global_variable)

bar()

666

def bar2():
    global_variable = 42

bar2()

global_variable

666

def bar3():
    global global_variable
    global_variable = 42

bar3()

global_variable

42

def bar4(param=42):
    print(param)

bar4(666)

666

bar4()

42

def bar5(param=[]):
    print(param)

bar5(42)

42

bar5()

[]

def bar6(param=[]):
    param.append(666)
    print(param)

bar6()

[666]

bar6()

[666, 666]

dir(bar6)

['__annotations__',
 '__builtins__',
 '__call__',
 '__class__',
 '__closure__',
 '__code__',
 '__defaults__',
 '__delattr__',
 '__dict__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__get__',
 '__getattribute__',
 '__globals__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__kwdefaults__',
 '__le__',
 '__lt__',
 '__module__',
 '__name__',
 '__ne__',
 '__new__',
 '__qualname__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__']

bar6.__defaults__

([666, 666],)

bar6()

[666, 666, 666]

bar6()

[666, 666, 666, 666]

bar6([42])

[42, 666]

bar6()

[666, 666, 666, 666, 666]

l = [42]
bar6(l)

[42, 666]

l

[42, 666]

And ``yield``?

def f():
    return 42
    return 666

f()

42

type(f)

function

def f():
    yield 42
    yield 666

type(f)

function

f()

<generator object f at 0x7fe7f869b7d0>

gen = f()

gen

<generator object f at 0x7fe7f869b920>

for i in gen:
    print(i)

42
666

def f():
    print('start, yielding 42')
    yield 42
    print('after yield 42, yielding 666')
    yield 666
    print('after yield 666')

gen = f()
gen

<generator object f at 0x7fe7f869bbc0>

for i in gen:
    print(i)

start, yielding 42
42
after yield 42, yielding 666
666
after yield 666

gen = f()

it = iter(gen)

next(it)

start, yielding 42

42

next(it)

after yield 42, yielding 666

666

try:
    next(it)
except Exception as e:
    print(e, type(e))

after yield 666
 <class 'StopIteration'>

Miscellaneous String Methods

s = 'abc'

print(type(s))

<class 'str'>

help(str)

Help on class str in module builtins:

class str(object)
 |  str(object='') -> str
 |  str(bytes_or_buffer[, encoding[, errors]]) -> str
 |
 |  Create a new string object from the given object. If encoding or
 |  errors is specified, then the object must expose a data buffer
 |  that will be decoded using the given encoding and error handler.
 |  Otherwise, returns the result of object.__str__() (if defined)
 |  or repr(object).
 |  encoding defaults to sys.getdefaultencoding().
 |  errors defaults to 'strict'.
 |
 |  Methods defined here:
 |
 |  __add__(self, value, /)
 |      Return self+value.
 |
 |  __contains__(self, key, /)
 |      Return key in self.
 |
 |  __eq__(self, value, /)
 |      Return self==value.
 |
 |  __format__(self, format_spec, /)
 |      Return a formatted version of the string as described by format_spec.
 |
 |  __ge__(self, value, /)
 |      Return self>=value.
 |
 |  __getattribute__(self, name, /)
 |      Return getattr(self, name).
 |
 |  __getitem__(self, key, /)
 |      Return self[key].
 |
 |  __getnewargs__(...)
 |
 |  __gt__(self, value, /)
 |      Return self>value.
 |
 |  __hash__(self, /)
 |      Return hash(self).
 |
 |  __iter__(self, /)
 |      Implement iter(self).
 |
 |  __le__(self, value, /)
 |      Return self<=value.
 |
 |  __len__(self, /)
 |      Return len(self).
 |
 |  __lt__(self, value, /)
 |      Return self<value.
 |
 |  __mod__(self, value, /)
 |      Return self%value.
 |
 |  __mul__(self, value, /)
 |      Return self*value.
 |
 |  __ne__(self, value, /)
 |      Return self!=value.
 |
 |  __repr__(self, /)
 |      Return repr(self).
 |
 |  __rmod__(self, value, /)
 |      Return value%self.
 |
 |  __rmul__(self, value, /)
 |      Return value*self.
 |
 |  __sizeof__(self, /)
 |      Return the size of the string in memory, in bytes.
 |
 |  __str__(self, /)
 |      Return str(self).
 |
 |  capitalize(self, /)
 |      Return a capitalized version of the string.
 |
 |      More specifically, make the first character have upper case and the rest lower
 |      case.
 |
 |  casefold(self, /)
 |      Return a version of the string suitable for caseless comparisons.
 |
 |  center(self, width, fillchar=' ', /)
 |      Return a centered string of length width.
 |
 |      Padding is done using the specified fill character (default is a space).
 |
 |  count(...)
 |      S.count(sub[, start[, end]]) -> int
 |
 |      Return the number of non-overlapping occurrences of substring sub in
 |      string S[start:end].  Optional arguments start and end are
 |      interpreted as in slice notation.
 |
 |  encode(self, /, encoding='utf-8', errors='strict')
 |      Encode the string using the codec registered for encoding.
 |
 |      encoding
 |        The encoding in which to encode the string.
 |      errors
 |        The error handling scheme to use for encoding errors.
 |        The default is 'strict' meaning that encoding errors raise a
 |        UnicodeEncodeError.  Other possible values are 'ignore', 'replace' and
 |        'xmlcharrefreplace' as well as any other name registered with
 |        codecs.register_error that can handle UnicodeEncodeErrors.
 |
 |  endswith(...)
 |      S.endswith(suffix[, start[, end]]) -> bool
 |
 |      Return True if S ends with the specified suffix, False otherwise.
 |      With optional start, test S beginning at that position.
 |      With optional end, stop comparing S at that position.
 |      suffix can also be a tuple of strings to try.
 |
 |  expandtabs(self, /, tabsize=8)
 |      Return a copy where all tab characters are expanded using spaces.
 |
 |      If tabsize is not given, a tab size of 8 characters is assumed.
 |
 |  find(...)
 |      S.find(sub[, start[, end]]) -> int
 |
 |      Return the lowest index in S where substring sub is found,
 |      such that sub is contained within S[start:end].  Optional
 |      arguments start and end are interpreted as in slice notation.
 |
 |      Return -1 on failure.
 |
 |  format(...)
 |      S.format(*args, **kwargs) -> str
 |
 |      Return a formatted version of S, using substitutions from args and kwargs.
 |      The substitutions are identified by braces ('{' and '}').
 |
 |  format_map(...)
 |      S.format_map(mapping) -> str
 |
 |      Return a formatted version of S, using substitutions from mapping.
 |      The substitutions are identified by braces ('{' and '}').
 |
 |  index(...)
 |      S.index(sub[, start[, end]]) -> int
 |
 |      Return the lowest index in S where substring sub is found,
 |      such that sub is contained within S[start:end].  Optional
 |      arguments start and end are interpreted as in slice notation.
 |
 |      Raises ValueError when the substring is not found.
 |
 |  isalnum(self, /)
 |      Return True if the string is an alpha-numeric string, False otherwise.
 |
 |      A string is alpha-numeric if all characters in the string are alpha-numeric and
 |      there is at least one character in the string.
 |
 |  isalpha(self, /)
 |      Return True if the string is an alphabetic string, False otherwise.
 |
 |      A string is alphabetic if all characters in the string are alphabetic and there
 |      is at least one character in the string.
 |
 |  isascii(self, /)
 |      Return True if all characters in the string are ASCII, False otherwise.
 |
 |      ASCII characters have code points in the range U+0000-U+007F.
 |      Empty string is ASCII too.
 |
 |  isdecimal(self, /)
 |      Return True if the string is a decimal string, False otherwise.
 |
 |      A string is a decimal string if all characters in the string are decimal and
 |      there is at least one character in the string.
 |
 |  isdigit(self, /)
 |      Return True if the string is a digit string, False otherwise.
 |
 |      A string is a digit string if all characters in the string are digits and there
 |      is at least one character in the string.
 |
 |  isidentifier(self, /)
 |      Return True if the string is a valid Python identifier, False otherwise.
 |
 |      Call keyword.iskeyword(s) to test whether string s is a reserved identifier,
 |      such as "def" or "class".
 |
 |  islower(self, /)
 |      Return True if the string is a lowercase string, False otherwise.
 |
 |      A string is lowercase if all cased characters in the string are lowercase and
 |      there is at least one cased character in the string.
 |
 |  isnumeric(self, /)
 |      Return True if the string is a numeric string, False otherwise.
 |
 |      A string is numeric if all characters in the string are numeric and there is at
 |      least one character in the string.
 |
 |  isprintable(self, /)
 |      Return True if the string is printable, False otherwise.
 |
 |      A string is printable if all of its characters are considered printable in
 |      repr() or if it is empty.
 |
 |  isspace(self, /)
 |      Return True if the string is a whitespace string, False otherwise.
 |
 |      A string is whitespace if all characters in the string are whitespace and there
 |      is at least one character in the string.
 |
 |  istitle(self, /)
 |      Return True if the string is a title-cased string, False otherwise.
 |
 |      In a title-cased string, upper- and title-case characters may only
 |      follow uncased characters and lowercase characters only cased ones.
 |
 |  isupper(self, /)
 |      Return True if the string is an uppercase string, False otherwise.
 |
 |      A string is uppercase if all cased characters in the string are uppercase and
 |      there is at least one cased character in the string.
 |
 |  join(self, iterable, /)
 |      Concatenate any number of strings.
 |
 |      The string whose method is called is inserted in between each given string.
 |      The result is returned as a new string.
 |
 |      Example: '.'.join(['ab', 'pq', 'rs']) -> 'ab.pq.rs'
 |
 |  ljust(self, width, fillchar=' ', /)
 |      Return a left-justified string of length width.
 |
 |      Padding is done using the specified fill character (default is a space).
 |
 |  lower(self, /)
 |      Return a copy of the string converted to lowercase.
 |
 |  lstrip(self, chars=None, /)
 |      Return a copy of the string with leading whitespace removed.
 |
 |      If chars is given and not None, remove characters in chars instead.
 |
 |  partition(self, sep, /)
 |      Partition the string into three parts using the given separator.
 |
 |      This will search for the separator in the string.  If the separator is found,
 |      returns a 3-tuple containing the part before the separator, the separator
 |      itself, and the part after it.
 |
 |      If the separator is not found, returns a 3-tuple containing the original string
 |      and two empty strings.
 |
 |  removeprefix(self, prefix, /)
 |      Return a str with the given prefix string removed if present.
 |
 |      If the string starts with the prefix string, return string[len(prefix):].
 |      Otherwise, return a copy of the original string.
 |
 |  removesuffix(self, suffix, /)
 |      Return a str with the given suffix string removed if present.
 |
 |      If the string ends with the suffix string and that suffix is not empty,
 |      return string[:-len(suffix)]. Otherwise, return a copy of the original
 |      string.
 |
 |  replace(self, old, new, count=-1, /)
 |      Return a copy with all occurrences of substring old replaced by new.
 |
 |        count
 |          Maximum number of occurrences to replace.
 |          -1 (the default value) means replace all occurrences.
 |
 |      If the optional argument count is given, only the first count occurrences are
 |      replaced.
 |
 |  rfind(...)
 |      S.rfind(sub[, start[, end]]) -> int
 |
 |      Return the highest index in S where substring sub is found,
 |      such that sub is contained within S[start:end].  Optional
 |      arguments start and end are interpreted as in slice notation.
 |
 |      Return -1 on failure.
 |
 |  rindex(...)
 |      S.rindex(sub[, start[, end]]) -> int
 |
 |      Return the highest index in S where substring sub is found,
 |      such that sub is contained within S[start:end].  Optional
 |      arguments start and end are interpreted as in slice notation.
 |
 |      Raises ValueError when the substring is not found.
 |
 |  rjust(self, width, fillchar=' ', /)
 |      Return a right-justified string of length width.
 |
 |      Padding is done using the specified fill character (default is a space).
 |
 |  rpartition(self, sep, /)
 |      Partition the string into three parts using the given separator.
 |
 |      This will search for the separator in the string, starting at the end. If
 |      the separator is found, returns a 3-tuple containing the part before the
 |      separator, the separator itself, and the part after it.
 |
 |      If the separator is not found, returns a 3-tuple containing two empty strings
 |      and the original string.
 |
 |  rsplit(self, /, sep=None, maxsplit=-1)
 |      Return a list of the substrings in the string, using sep as the separator string.
 |
 |        sep
 |          The separator used to split the string.
 |
 |          When set to None (the default value), will split on any whitespace
 |          character (including \\n \\r \\t \\f and spaces) and will discard
 |          empty strings from the result.
 |        maxsplit
 |          Maximum number of splits (starting from the left).
 |          -1 (the default value) means no limit.
 |
 |      Splitting starts at the end of the string and works to the front.
 |
 |  rstrip(self, chars=None, /)
 |      Return a copy of the string with trailing whitespace removed.
 |
 |      If chars is given and not None, remove characters in chars instead.
 |
 |  split(self, /, sep=None, maxsplit=-1)
 |      Return a list of the substrings in the string, using sep as the separator string.
 |
 |        sep
 |          The separator used to split the string.
 |
 |          When set to None (the default value), will split on any whitespace
 |          character (including \\n \\r \\t \\f and spaces) and will discard
 |          empty strings from the result.
 |        maxsplit
 |          Maximum number of splits (starting from the left).
 |          -1 (the default value) means no limit.
 |
 |      Note, str.split() is mainly useful for data that has been intentionally
 |      delimited.  With natural text that includes punctuation, consider using
 |      the regular expression module.
 |
 |  splitlines(self, /, keepends=False)
 |      Return a list of the lines in the string, breaking at line boundaries.
 |
 |      Line breaks are not included in the resulting list unless keepends is given and
 |      true.
 |
 |  startswith(...)
 |      S.startswith(prefix[, start[, end]]) -> bool
 |
 |      Return True if S starts with the specified prefix, False otherwise.
 |      With optional start, test S beginning at that position.
 |      With optional end, stop comparing S at that position.
 |      prefix can also be a tuple of strings to try.
 |
 |  strip(self, chars=None, /)
 |      Return a copy of the string with leading and trailing whitespace removed.
 |
 |      If chars is given and not None, remove characters in chars instead.
 |
 |  swapcase(self, /)
 |      Convert uppercase characters to lowercase and lowercase characters to uppercase.
 |
 |  title(self, /)
 |      Return a version of the string where each word is titlecased.
 |
 |      More specifically, words start with uppercased characters and all remaining
 |      cased characters have lower case.
 |
 |  translate(self, table, /)
 |      Replace each character in the string using the given translation table.
 |
 |        table
 |          Translation table, which must be a mapping of Unicode ordinals to
 |          Unicode ordinals, strings, or None.
 |
 |      The table must implement lookup/indexing via __getitem__, for instance a
 |      dictionary or list.  If this operation raises LookupError, the character is
 |      left untouched.  Characters mapped to None are deleted.
 |
 |  upper(self, /)
 |      Return a copy of the string converted to uppercase.
 |
 |  zfill(self, width, /)
 |      Pad a numeric string with zeros on the left, to fill a field of the given width.
 |
 |      The string is never truncated.
 |
 |  ----------------------------------------------------------------------
 |  Static methods defined here:
 |
 |  __new__(*args, **kwargs) from builtins.type
 |      Create and return a new object.  See help(type) for accurate signature.
 |
 |  maketrans(...)
 |      Return a translation table usable for str.translate().
 |
 |      If there is only one argument, it must be a dictionary mapping Unicode
 |      ordinals (integers) or characters to Unicode ordinals, strings or None.
 |      Character keys will be then converted to ordinals.
 |      If there are two arguments, they must be strings of equal length, and
 |      in the resulting dictionary, each character in x will be mapped to the
 |      character at the same position in y. If there is a third argument, it
 |      must be a string, whose characters will be mapped to None in the result.

s*5

'abcabcabcabcabc'

s.__sizeof__()

52

'abcd'.__sizeof__()

53

s.__len__()

3

len(s)

3

s.__gt__('aaa')

True

s > 'aaa'

True

s.capitalize()

'Abc'

s

'abc'

s = 'mississippi'

s.count('ss')

2

s.count('i')

4

s.upper()

'MISSISSIPPI'

s.upper().lower()

'mississippi'

filename = 'blah.csv'

filename.endswith('.csv')

True

filename.startswith('xx')

False

s

'mississippi'

s.find('ss')

2

s.find('ss', 3)

5

s.find('ss', s.find('ss')+1)

5

s.find('xx')

-1

s.index('ss')

2

try:
    s.index('xx')
except ValueError as e:
    print(e, type(e))

substring not found <class 'ValueError'>

line = '5;Joerg;Faschingbauer'

line.split(';')

['5', 'Joerg', 'Faschingbauer']

line.split(';', 1)

['5', 'Joerg;Faschingbauer']

fields = ['5', 'Joerg', 'Faschingbauer']

';'.join(fields)

'5;Joerg;Faschingbauer'

'abc'.center(50)

'                       abc                        '

line = '    \n     abc     \t   '

line.strip()

'abc'

line.strip(' ')

'\n     abc     \t'

line.rstrip()

'    \n     abc'

line.lstrip()

'abc     \t   '

import re

line = 'ss ss ss 1234'

rex = re.compile(r'^ss\s+ss\s+ss\s+(\d+)\s*$')

match = rex.search(line)

print(match)

<re.Match object; span=(0, 13), match='ss ss ss 1234'>

match.group(1)

'1234'

Lists

l = [3,2,4,5,1,]
l.sort()

l

[1, 2, 3, 4, 5]

l = [3,2,4,5,1,]
sorted(l)

[1, 2, 3, 4, 5]

l

[3, 2, 4, 5, 1]

sorted('cba')

['a', 'b', 'c']

Dictionaries

d = {'one': 1, 'two': 2}
d

{'one': 1, 'two': 2}

d = {}

l = [('one', 1), ('two', 2)]
d = dict(l)
d

{'one': 1, 'two': 2}

d['one']

1

try:
    d['three']
except Exception as e:
    print(e, type(e))

'three' <class 'KeyError'>

d.get('two')

2

value = d.get('three')
print(value)

None

value = d.get('three')
if value is None:
    print(3)
else:
    print(value)

3

d.get('three', 3)

3

d

{'one': 1, 'two': 2}

if 'three' in d:
    value = d['three']
else:
    d['three'] = 3
    value = d['three']
print(value)

3

d.setdefault('three', 3)

3

d

{'one': 1, 'two': 2, 'three': 3}

another_d = {'three': 3.0, 'four': 4.0, 'five': 5}

d.update(another_d)
d

{'one': 1, 'two': 2, 'three': 3.0, 'four': 4.0, 'five': 5}

x = 666
x

666

del x

try:
    x
except Exception as e:
    print(e, type(e))

name 'x' is not defined <class 'NameError'>

d

{'one': 1, 'two': 2, 'three': 3.0, 'four': 4.0, 'five': 5}

del d['three']

d

{'one': 1, 'two': 2, 'four': 4.0, 'five': 5}

for elem in d:
    print(elem)

one
two
four
five

for elem in d.keys():
    print(elem)

one
two
four
five

for elem in d.values():
    print(elem)

1
2
4.0
5

for elem in d.items():
    print(elem)

('one', 1)
('two', 2)
('four', 4.0)
('five', 5)

for elem in d.items():
    key = elem[0]
    value = elem[1]
    print(f'key {key}, value {value}')

key one, value 1
key two, value 2
key four, value 4.0
key five, value 5

for key, value in d.items():
    print(f'key {key}, value {value}')

key one, value 1
key two, value 2
key four, value 4.0
key five, value 5

Good ol’ format():

'key {key}, value {value}'.format(key=3, value='three')

'key 3, value three'

'key {0}, value {1}'.format(3, 'three')

'key 3, value three'

File I/O

f = open('/etc/passwd')

f

<_io.TextIOWrapper name='/etc/passwd' mode='r' encoding='UTF-8'>

f.close()

with open('/etc/passwd') as f:
    pass

f = open('/etc/passwd', encoding='ascii')

try:
    f.read()
except Exception as e:
    print(e, type(e))

f = open('/etc/passwd', encoding='utf-8')

f.read()

'root:x:0:0:root:/root:/bin/bash\nbin:x:1:1:bin:/bin:/sbin/nologin\ndaemon:x:2:2:daemon:/sbin:/sbin/nologin\nadm:x:3:4:adm:/var/adm:/sbin/nologin\nlp:x:4:7:lp:/var/spool/lpd:/sbin/nologin\nsync:x:5:0:sync:/sbin:/bin/sync\nshutdown:x:6:0:shutdown:/sbin:/sbin/shutdown\nhalt:x:7:0:halt:/sbin:/sbin/halt\nmail:x:8:12:mail:/var/spool/mail:/sbin/nologin\noperator:x:11:0:operator:/root:/sbin/nologin\ngames:x:12:100:games:/usr/games:/sbin/nologin\nftp:x:14:50:FTP User:/var/ftp:/sbin/nologin\nnobody:x:65534:65534:Kernel Overflow User:/:/sbin/nologin\ndbus:x:81:81:System message bus:/:/sbin/nologin\napache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin\ntss:x:59:59:Account used for TPM access:/dev/null:/sbin/nologin\nsystemd-network:x:192:192:systemd Network Management:/:/usr/sbin/nologin\nsystemd-oom:x:999:999:systemd Userspace OOM Killer:/:/usr/sbin/nologin\nsystemd-resolve:x:193:193:systemd Resolver:/:/usr/sbin/nologin\nqemu:x:107:107:qemu user:/:/sbin/nologin\npolkitd:x:998:997:User for polkitd:/:/sbin/nologin\navahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin\nunbound:x:997:995:Unbound DNS resolver:/etc/unbound:/sbin/nologin\nnm-openconnect:x:996:994:NetworkManager user for OpenConnect:/:/sbin/nologin\ngeoclue:x:995:993:User for geoclue:/var/lib/geoclue:/sbin/nologin\nusbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin\ngluster:x:994:992:GlusterFS daemons:/run/gluster:/sbin/nologin\nrtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin\nchrony:x:993:990::/var/lib/chrony:/sbin/nologin\nsaslauth:x:992:76:Saslauthd user:/run/saslauthd:/sbin/nologin\ndnsmasq:x:991:989:Dnsmasq DHCP and DNS server:/var/lib/dnsmasq:/sbin/nologin\nrpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin\ncolord:x:990:988:User for colord:/var/lib/colord:/sbin/nologin\nrpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin\nopenvpn:x:989:987:OpenVPN:/etc/openvpn:/sbin/nologin\nnm-openvpn:x:988:986:Default user for running openvpn spawned by NetworkManager:/:/sbin/nologin\npipewire:x:987:985:PipeWire System Daemon:/var/run/pipewire:/sbin/nologin\nabrt:x:173:173::/etc/abrt:/sbin/nologin\nflatpak:x:986:983:User for flatpak system helper:/:/sbin/nologin\ngdm:x:42:42:GNOME Display Manager:/var/lib/gdm:/sbin/nologin\ngnome-initial-setup:x:985:982::/run/gnome-initial-setup/:/sbin/nologin\nvboxadd:x:984:1::/var/run/vboxadd:/sbin/nologin\nsshd:x:74:74:Privilege-separated SSH:/usr/share/empty.sshd:/sbin/nologin\ntcpdump:x:72:72::/:/sbin/nologin\njfasch:x:1000:1000:Jörg Faschingbauer:/home/jfasch:/bin/bash\nsystemd-coredump:x:978:978:systemd Core Dumper:/:/usr/sbin/nologin\nsystemd-timesync:x:977:977:systemd Time Synchronization:/:/usr/sbin/nologin\nmosquitto:x:976:976:Mosquitto Broker:/etc/mosquitto:/sbin/nologin\n'

f = open('/etc/passwd', 'rb')

f.read()

b'root:x:0:0:root:/root:/bin/bash\nbin:x:1:1:bin:/bin:/sbin/nologin\ndaemon:x:2:2:daemon:/sbin:/sbin/nologin\nadm:x:3:4:adm:/var/adm:/sbin/nologin\nlp:x:4:7:lp:/var/spool/lpd:/sbin/nologin\nsync:x:5:0:sync:/sbin:/bin/sync\nshutdown:x:6:0:shutdown:/sbin:/sbin/shutdown\nhalt:x:7:0:halt:/sbin:/sbin/halt\nmail:x:8:12:mail:/var/spool/mail:/sbin/nologin\noperator:x:11:0:operator:/root:/sbin/nologin\ngames:x:12:100:games:/usr/games:/sbin/nologin\nftp:x:14:50:FTP User:/var/ftp:/sbin/nologin\nnobody:x:65534:65534:Kernel Overflow User:/:/sbin/nologin\ndbus:x:81:81:System message bus:/:/sbin/nologin\napache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin\ntss:x:59:59:Account used for TPM access:/dev/null:/sbin/nologin\nsystemd-network:x:192:192:systemd Network Management:/:/usr/sbin/nologin\nsystemd-oom:x:999:999:systemd Userspace OOM Killer:/:/usr/sbin/nologin\nsystemd-resolve:x:193:193:systemd Resolver:/:/usr/sbin/nologin\nqemu:x:107:107:qemu user:/:/sbin/nologin\npolkitd:x:998:997:User for polkitd:/:/sbin/nologin\navahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin\nunbound:x:997:995:Unbound DNS resolver:/etc/unbound:/sbin/nologin\nnm-openconnect:x:996:994:NetworkManager user for OpenConnect:/:/sbin/nologin\ngeoclue:x:995:993:User for geoclue:/var/lib/geoclue:/sbin/nologin\nusbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin\ngluster:x:994:992:GlusterFS daemons:/run/gluster:/sbin/nologin\nrtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin\nchrony:x:993:990::/var/lib/chrony:/sbin/nologin\nsaslauth:x:992:76:Saslauthd user:/run/saslauthd:/sbin/nologin\ndnsmasq:x:991:989:Dnsmasq DHCP and DNS server:/var/lib/dnsmasq:/sbin/nologin\nrpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin\ncolord:x:990:988:User for colord:/var/lib/colord:/sbin/nologin\nrpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin\nopenvpn:x:989:987:OpenVPN:/etc/openvpn:/sbin/nologin\nnm-openvpn:x:988:986:Default user for running openvpn spawned by NetworkManager:/:/sbin/nologin\npipewire:x:987:985:PipeWire System Daemon:/var/run/pipewire:/sbin/nologin\nabrt:x:173:173::/etc/abrt:/sbin/nologin\nflatpak:x:986:983:User for flatpak system helper:/:/sbin/nologin\ngdm:x:42:42:GNOME Display Manager:/var/lib/gdm:/sbin/nologin\ngnome-initial-setup:x:985:982::/run/gnome-initial-setup/:/sbin/nologin\nvboxadd:x:984:1::/var/run/vboxadd:/sbin/nologin\nsshd:x:74:74:Privilege-separated SSH:/usr/share/empty.sshd:/sbin/nologin\ntcpdump:x:72:72::/:/sbin/nologin\njfasch:x:1000:1000:J\xc3\xb6rg Faschingbauer:/home/jfasch:/bin/bash\nsystemd-coredump:x:978:978:systemd Core Dumper:/:/usr/sbin/nologin\nsystemd-timesync:x:977:977:systemd Time Synchronization:/:/usr/sbin/nologin\nmosquitto:x:976:976:Mosquitto Broker:/etc/mosquitto:/sbin/nologin\n'

f.close()

f = open('/etc/passwd', encoding='utf-8')

f.read(10)

'root:x:0:0'

f.read(10)

':root:/roo'

_ = f.read(2640)

len(_)

2640

s = f.read(30000)

len(s)

30

s = f.read(3000)

len(s)

0

f.seek(0)

0

f.read(10)

'root:x:0:0'

f = open('/etc/passwd', encoding = 'utf-8')

for line in f:
    print(line)

root:x:0:0:root:/root:/bin/bash

bin:x:1:1:bin:/bin:/sbin/nologin

daemon:x:2:2:daemon:/sbin:/sbin/nologin

adm:x:3:4:adm:/var/adm:/sbin/nologin

lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin

sync:x:5:0:sync:/sbin:/bin/sync

shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown

halt:x:7:0:halt:/sbin:/sbin/halt

mail:x:8:12:mail:/var/spool/mail:/sbin/nologin

operator:x:11:0:operator:/root:/sbin/nologin

games:x:12:100:games:/usr/games:/sbin/nologin

ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin

nobody:x:65534:65534:Kernel Overflow User:/:/sbin/nologin

dbus:x:81:81:System message bus:/:/sbin/nologin

apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

tss:x:59:59:Account used for TPM access:/dev/null:/sbin/nologin

systemd-network:x:192:192:systemd Network Management:/:/usr/sbin/nologin

systemd-oom:x:999:999:systemd Userspace OOM Killer:/:/usr/sbin/nologin

systemd-resolve:x:193:193:systemd Resolver:/:/usr/sbin/nologin

qemu:x:107:107:qemu user:/:/sbin/nologin

polkitd:x:998:997:User for polkitd:/:/sbin/nologin

avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin

unbound:x:997:995:Unbound DNS resolver:/etc/unbound:/sbin/nologin

nm-openconnect:x:996:994:NetworkManager user for OpenConnect:/:/sbin/nologin

geoclue:x:995:993:User for geoclue:/var/lib/geoclue:/sbin/nologin

usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin

gluster:x:994:992:GlusterFS daemons:/run/gluster:/sbin/nologin

rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin

chrony:x:993:990::/var/lib/chrony:/sbin/nologin

saslauth:x:992:76:Saslauthd user:/run/saslauthd:/sbin/nologin

dnsmasq:x:991:989:Dnsmasq DHCP and DNS server:/var/lib/dnsmasq:/sbin/nologin

rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin

colord:x:990:988:User for colord:/var/lib/colord:/sbin/nologin

rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin

openvpn:x:989:987:OpenVPN:/etc/openvpn:/sbin/nologin

nm-openvpn:x:988:986:Default user for running openvpn spawned by NetworkManager:/:/sbin/nologin

pipewire:x:987:985:PipeWire System Daemon:/var/run/pipewire:/sbin/nologin

abrt:x:173:173::/etc/abrt:/sbin/nologin

flatpak:x:986:983:User for flatpak system helper:/:/sbin/nologin

gdm:x:42:42:GNOME Display Manager:/var/lib/gdm:/sbin/nologin

gnome-initial-setup:x:985:982::/run/gnome-initial-setup/:/sbin/nologin

vboxadd:x:984:1::/var/run/vboxadd:/sbin/nologin

sshd:x:74:74:Privilege-separated SSH:/usr/share/empty.sshd:/sbin/nologin

tcpdump:x:72:72::/:/sbin/nologin

jfasch:x:1000:1000:Jörg Faschingbauer:/home/jfasch:/bin/bash

systemd-coredump:x:978:978:systemd Core Dumper:/:/usr/sbin/nologin

systemd-timesync:x:977:977:systemd Time Synchronization:/:/usr/sbin/nologin

mosquitto:x:976:976:Mosquitto Broker:/etc/mosquitto:/sbin/nologin

CSV

d = {
    'ID': '5',
    'Firstname': 'Joerg',
    'Lastname': 'Faschingbauer',
}

id, firstname, lastname = d

id, firstname, lastname

('ID', 'Firstname', 'Lastname')

for elem in d:
    print(elem)

ID
Firstname
Lastname

Lambda, And Functional Programming Tools

def square(n): return n**2

l = [0,1,2,3,4,5]

for elem in l:
    print(square(elem))

0
1
4
9
16
25

for sq in map(square, l):
    print(sq)

0
1
4
9
16
25

for sq in map(lambda n: n**2, l):
    print(sq)

0
1
4
9
16
25

for sq in map(lambda n: n**2, range(6)):
    print(sq)

0
1
4
9
16
25

for even in filter(lambda n: n%2==0, range(6)):
    print(even)

0
2
4

for sq in (n**2 for n in range(6)):
    print(sq)

0
1
4
9
16
25

for even in (n for n in range(6) if n%2 == 0):
    print(even)

0
2
4